hi i had gone through your query and understand your concerns. i would come up with the possibility of FLATULENT DYSPEPSIA
or ACID PEPTIC DYSPEPSIA may be the cause for his sufferings.
-either excessive acid secretion or diminished mucosal defense may cause this condition
-infection with Helicobacter
-eating spicy,junk food
-taking too much pain killers
are some causes
I hope this is helpful for you, thank you